Examination of the requirement for ucp-4, a putative homolog of mammalian uncoupling proteins, for stress tolerance and longevity in C. elegans.
ABSTRACT Reactive oxygen species (ROS) are generated by mitochondrial respiration and can react with and damage cellular components. According to the free radical theory of aging, oxidative damage from mitochondrial ROS is a major cause of cellular decline during aging. Mitochondrial uncoupling proteins (UCPs) uncouple ATP production from electron transport and can be stimulated by free radicals, suggesting UCPs may perform a cytoprotective function. The nematode, Caenorhabditis elegans, contains one UCP-like protein, encoded by the ucp-4 gene. We have investigated the genetic requirement for ucp-4 in normal aging and stress resistance. Consistent with the hypothesis that ucp-4 encodes a putative uncoupling protein, animals lacking ucp-4 function contained elevated ATP levels. However, the absence of ucp-4 function did not affect adult lifespan or survival in the presence of thermal or oxidative stress. Together, these results demonstrate that ucp-4 is a negative regulator of ATP production in C. elegans, but is not required for normal lifespan.
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ABSTRACT: We have taken an engineering approach to extending the lifespan of Caenorhabditis elegans. Aging stands out as a complex trait, because events that occur in old animals are not under strong natural selection. As a result, lifespan can be lengthened rationally using bioengineering to modulate gene expression or to add exogenous components. Here, we engineered longer lifespan by expressing genes from zebrafish encoding molecular functions not normally present in worms. Additionally, we extended lifespan by increasing the activity of four endogenous worm aging pathways. Next, we used a modular approach to extend lifespan by combining components. Finally, we used cell- and worm-based assays to analyze changes in cell physiology and as a rapid means to evaluate whether multi-component transgenic lines were likely to have extended longevity. Using engineering to add novel functions and to tune endogenous functions provides a new framework for lifespan extension that goes beyond the constraints of the worm genome.PLoS Genetics 06/2012; 8(6):e1002780. · 8.69 Impact Factor
Article: Disruption of insulin signalling preserves bioenergetic competence of mitochondria in ageing Caenorhabditis elegans.[show abstract] [hide abstract]
ABSTRACT: The gene daf-2 encodes the single insulin/insulin growth factor-1-like receptor of Caenorhabditis elegans. The reduction-of-function allele e1370 induces several metabolic alterations and doubles lifespan. We found that the e1370 mutation alters aerobic energy production substantially. In wild-type worms the abundance of key mitochondrial proteins declines with age, accompanied by a dramatic decrease in energy production, although the mitochondrial mass, inferred from the mitochondrial DNA copy number, remains unaltered. In contrast, the age-dependent decrease of both key mitochondrial proteins and bioenergetic competence is considerably attenuated in daf-2(e1370) adult animals. The increase in daf-2(e1370) mitochondrial competence is associated with a higher membrane potential and increased reactive oxygen species production, but with little damage to mitochondrial protein or DNA. Together these results point to a higher energetic efficiency of daf-2(e1370) animals. We conclude that low daf-2 function alters the overall rate of ageing by a yet unidentified mechanism with an indirect protective effect on mitochondrial function.BMC Biology 01/2010; 8:91. · 5.75 Impact Factor
Article: Mitochondrial changes in ageing Caenorhabditis elegans--what do we learn from superoxide dismutase knockouts?[show abstract] [hide abstract]
ABSTRACT: One of the most popular damage accumulation theories of ageing is the mitochondrial free radical theory of ageing (mFRTA). The mFRTA proposes that ageing is due to the accumulation of unrepaired oxidative damage, in particular damage to mitochondrial DNA (mtDNA). Within the mFRTA, the "vicious cycle" theory further proposes that reactive oxygen species (ROS) promote mtDNA mutations, which then lead to a further increase in ROS production. Recently, data have been published on Caenorhabditis elegans mutants deficient in one or both forms of mitochondrial superoxide dismutase (SOD). Surprisingly, even double mutants, lacking both mitochondrial forms of SOD, show no reduction in lifespan. This has been interpreted as evidence against the mFRTA because it is assumed that these mutants suffer from significantly elevated oxidative damage to their mitochondria. Here, using a novel mtDNA damage assay in conjunction with related, well established damage and metabolic markers, we first investigate the age-dependent mitochondrial decline in a cohort of ageing wild-type nematodes, in particular testing the plausibility of the "vicious cycle" theory. We then apply the methods and insights gained from this investigation to a mutant strain for C. elegans that lacks both forms of mitochondrial SOD. While we show a clear age-dependent, linear increase in oxidative damage in WT nematodes, we find no evidence for autocatalytic damage amplification as proposed by the "vicious cycle" theory. Comparing the SOD mutants with wild-type animals, we further show that oxidative damage levels in the mtDNA of SOD mutants are not significantly different from those in wild-type animals, i.e. even the total loss of mitochondrial SOD did not significantly increase oxidative damage to mtDNA. Possible reasons for this unexpected result and some implications for the mFRTA are discussed.PLoS ONE 01/2011; 6(5):e19444. · 4.09 Impact Factor